Anthony Miller couldn’t believe his eyes. It was late in the fourth quarter of a tie game in South Florida on Sunday and yet as Miller took off out of the slot on a crucial third-down play, the Dolphins defense left him uncovered. Just a speedy rookie sprinting through green grass, his eyes widening with every step.

“I just focused on catching the ball,” Miller said. “All I wanted to do was secure that ball.”

Dolphins defensive coordinator Matt Burke had called for a blitz, sending seven defenders at Mitch Trubisky. That included rookie safety Minkah Fitzpatrick, who had been matched up with Miller before the snap.

“They were going to try to heat us up there,” Bears coach Matt Nagy said.

But the Bears offense had its counterpunch. With the Dolphins’ lone deep safety shading to his left, the middle of the field was open. All Trubisky needed was recognition. And the proper time.

The Bears’ protection was sturdy. Trubisky took his drop without disruption. And when linebacker Jerome Baker experienced a moment of confusion while dropping into coverage, Miller broke free.

Easy read, easy throw. Easy catch. Easy touchdown.

“The line bought me enough time,” Trubisky said Wednesday at Halas Hall. “I confirmed what I saw pre-snap. And I just gave Anthony a shot. He made a great play down the middle.”

Said Miller: “I enjoyed that moment.”

At the time, the whole sequence felt enormous. As Miller danced in the end zone, the Bears had responded to a pressure-packed moment with aplomb. They had taken a 28-21 lead. They had produced what appeared to be a clutch game-winning touchdown drive.

This was a young quarterback and a rookie receiver providing the exclamation point — a 29-yard touchdown to cap an 11-play, 75-yard drive.

Late in the fourth quarter. In a tie game. On the road.

Miller’s catch was the fourth third-down conversion on the possession.

“That’s a big moment for our guys to step up,” Nagy said. “That’s the growth of an offense.”

If you get lost in Sunday’s result — a galling 31-28 overtime loss — you’ll miss such important signs of progress, the growth Nagy and his players are seeing that will give them a chance to pull off an upset of the Patriots at Soldier Field this weekend.

On Wednesday, Patriots coach Bill Belichick offered his progress report on the Bears offense from afar.

“They’re pretty good, period,” Belichick said. “Like any team, as you go through the year your execution level gets better. Your timing (gets better). … You start putting little things together and doing it better. And the more things you do right, the better your chances are for success.”

In particular, Belichick singled out Trubisky’s 47-yard deep ball to Taylor Gabriel against the Dolphins, a first-half bomb that featured a precise pass and a highlight-reel grab.

“That’s about as good of a throw and catch as I’ve seen all year,” Belichick said. “The execution level on that is like 99 out of 100. It was a great throw. A great route. A great catch. There were like a few inches to get the ball in there 50 yards downfield and that’s where it was.”

That was one of many promising signs for the Bears on Sunday in what turned out to be a spirit-crushing loss. After struggling through a scoreless and mostly clunky first half in Miami, the offense found ways to come alive. After halftime, they scored 28 points and gained 343 yards. They scored touchdowns on three consecutive third-quarter possessions — quick-strike drives that averaged 54 seconds apiece.

At halftime, Trubisky sensed a hunger from his offense, a belief that the Bears have the playmakers and the system to get things rolling.

“We responded the right way,” he said. “We had conversations in the locker room about what we needed to do. It wasn’t necessarily anything they were doing on defense. It was more of what we weren’t doing on offense.

“It takes 11 guys all the time. And it really comes down to that mindset and that want-to.”

With the right mentality, the Bears found their rhythm and continued their development process. Then, in a big moment, late in a tie game, they marched down the field with confidence and put the ball in the end zone.

“The growth we showed was huge,” tight end Trey Burton said. “I don’t know if we would have done that (previously). We didn’t do that Week 1 (against the Packers). So you do see growth. You see guys maturing and playing at a high level and it’s fun to be a part of.”

Another big test waits Sunday — against a strong opponent and one of the best defensive strategists the sport ever has seen. The Bears are eager for the challenge. They sense they’re headed in the right direction. The push for improvement continues with a heightened level of enthusiasm.